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3H‐Phosphaallenes Revisited: Facile Synthesis by Hydroalumination of Alkynylphosphines and β‐Elimination, Stability and Trapping of Transient Species by Coordination to Transition Metal Atoms
Author(s) -
Klöcker Hans,
Tendyck Jonas C.,
Keweloh Lukas,
Hepp Alexander,
Uhl Werner
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201806334
Subject(s) - steric effects , chemistry , transition metal , tungsten , medicinal chemistry , aryl , decomposition , aryne , stereochemistry , organic chemistry , catalysis , alkyl
A facile method for the efficient synthesis of 3H‐phosphaallenes, R−P=C=C(H)−R′, is presented, which comprises treatment of dialkynylphosphines with dialkylaluminium hydrides (hydroalumination) and elimination of aluminium alkynides from intermediate alkenyl‐alkynylphosphines. The stability of the phosphaallenes depends on steric shielding by the substituents at phosphorus (aryl or CH(SiMe 3 ) 2 groups). Only supermesityl compounds are persistent at room temperature in solution. This simple method starting with easily accessible dialkynylphosphines and commercially available aluminium hydrides (HAlEt 2 , HAl i Bu 2 ) allows the generation of transient species, which were trapped by coordination to transition metals. The η 1 ‐coordination via a P−W bond was observed for tungsten, while the side‐on coordination via the P=C bond resulted with platinum. Decomposition of the mesityl derivative yielded an unprecedented product, which may be formed by 1,3‐H shift to the P atom, hydrophosphination of the P=C bond of a second phosphaallene and formation of a P−P bond.